Manufacture of knives



Aug. 9, 1932.v M. MAAG ET Al. 1,870,817

MANUFACTURE 0F KNIVES Filed Nov. 1o. 1923 2 sheets-sheet 1` w MAX MAAQ Ro/.IRT SA omofv BY, #44W #TW EY Filed Nov. l0. 1928 2 Sheets-Sheet 2 am TGA/ o iff .NON

Patented Aug. 9, 1932 UNITED STATES vPATENT oFFlcE IAX HAAG, F ZURICH-SCHWAHENDINGEN, SWITZERLAND, AND IROPEBT SALOMON, 0F NEUILLY-SUB-SEINE-FRANCE, ASSIGNOBS T0 SOCIETE DVETUDES' DE MACHINES AFFUTEB., or rams, FRANCE MANUFACTUBE oF xurvns Application led November 10, 1928, Serial No. 318,327, and in November-83, 1927.

Our invention relates to an improvement in the manufacture of knives, such as safety razor blades,- and more particularly to a method of grinding the same and to an improvement in the art of operating bladesharpening machines.

An object of our invention is a razor blade having a perfectly sharp and acute edge and a method of producing such a blade without generating` in the course of the grinding-.or sharpening: operation any ridge'which would necessitate a cumbersome treatment to remove the ridge subsequent to the grindingoperation prfier.

The metho of sharpening knives, particu-` larly razor blades, which has generally. been in use prior to'our invention, involvesthe necessity of removing the ridge from the edge after the latter has been ground. After such removal, however, dull spots remain on the edge in dependence upon the thickness of the ridge and an elaborate subsequent polishing treatment is required to sharpen said dull spots in` order to obtain a sharp edge, which is ready for use. Our invention permits; of materially reducing this polishing step which does not only involve amaterial" time consumption, but affects the curvature of the edge faces in the immediate proximity of the edge in an unfavorable manner with the result that the edge is less`sha-rp than it would be with a practically uniform curvature throughout the entire area of the ground faces.

Thus` our novelv method permits the generation of a sharp edge free from any ridge be completely regenerated in 'a simple manner.

slight polishing treat- Our invention is based upon the following consideratlon: When a work piece is sub' -jecte'd to the operation of grinding or cutting r tools the latter exert, as a rule, a pressure on the material operated upon. Where they operate upon a thinedge of the work piece, the marginal zoneof said edge which on account of its reduced thiclmess is unable to resist the pressure, will yield and will 'be pressed back from the edge to form a" ridge which is no longer subjected to the tool and, therefore, is

not removed. Theconditions which accountl for the formation of a ridge, are always-prevailing in the marginal zone of a sharp edge, the rear face of -which is in an acute angle to the front operated on by the cutting or grinding tool .as is the case' with knives or slmilar l work pieces. yIt follows that the formation of a ridge can be prevented byproviding a support for the .marginal zoneA which suports the latter against the pressure-exerted y the tools. VOurinvention is based upon the `use of such a. blade. support rwhich is in intimate contact with the rear face of the edge, "throughout the entire area of the same up to the very edge, during the courseof thegrind- I ing process whereby any yielding of the mar-l ginal zone`and, consequently, the formation of any ridgeis avoided. In other words, wesupport the rear face of the edge in the course of thel grinding process, preferably y over 'its entire length, at least up to the line determinin the final situation of the cutting v edge of the lade so that the support is partly ground away together with the blade bearing against it. Ii t is regardour invention differs from the prior art in which the support bearing against the rear face was not olf together with the blade.

preferred embodiment of a grindin machine which is particularly welladapted or carrying out .our method of sharpening razor blades. It is to be understood, however, that our novel method may be carried out with inding machines of known construction for- 1nstancewith that shown and'described in the U. S. Patent No. 1,126,839.

In Fig. 1 we have shown a side view of the machine; Fig. 2 is a top view and Fig. 3

ground he drawings we have .illustrated al is a perspective partial view of the machine, the part situated left to line -m of Fig. 1 being broken away. Fig. 4 illustrates a razor blade and Fig. 5 is a diagram indicating the successive stages of our method.

The frame- 1 is provided with a horizontal guide slidably accommodating a carriage 3 having upwardly projecting arms forme with bearings 4 and 5 in which a horizontal shaft 6 is mounted to be freely rotatable.

Thevshaft 6 is provided with a shoulder-7 pivot 22.

and with a grinding disc 8.of abrasive material in contact therewith. Furthermore, two nut rings 10 and 1-1 are screwed upon a threaded portion of the shaft and arebearing against a pulley 9'to press the latter against the grinding disc 8. whereby the same is kept in frictional engagement with the shoulder T andthe disc 8 for common rotation.

In the recessed central part of frame 1 an auxiliary guide 12 is arranged and kept 1n place by means of a bolt 13 to adjustably accommodate a carrier 13 carrying a blade' holder 17, 18, 20. The carrier 13- is displaceable in longitudinal direction and may be arrested in any desired position by means of clamping screws 14 and 14. The ends of carrier 13 are formed with upwardly pro'-, jecting arms having two' pointed screws 15 and 16* inserted in axial registry. These screws serve to pivotally support ablock 17 and to keep the latter in a predetermined position. v

Attached to block 17 is an upwardly projecting spring leaf 20 carrying at its upper end a second block 18 which is integral with an upwardly`projecting blade holder part 19 co-operating with another blade holder part 21 hinged to block 18 by means of a (Fig. Both blade holder parts are adapted-to keep between them a razor blade 23 such as shown 1n Fig. 4 and. are for this purpose provided with a bolt 51 attached to the part" 19 and projecting througha hole in part 21 to receive a clamping nut 24. Furthermore, the part '19 1s provided with two pins 25 and 25. projecting through registering openings 1n part 21.

The blade 23 is slipped with its holes 52 and\ 52 ove'r these pins and, then, part 21 is folded over the blade and pressed thereupon by the nut 24 which is applied to the bolt 51. Thus it will be seen, that the' razor blade 23. is kept in upright operative position relative j a to the grinding wheel.

' Furthermore, a blade support is arranged on frame 1 to bear against the rear face of the Vedge to support the latter. At a part of the supporting face of the support is ground, away inV each cycle of operation, the support is preferably shiftable in the direction of its supporting face whereby successive portions of its surface may be brought into contact relation to the blade. i

In the embodiment shown the support is,

for this purpose, formed by a rotatable cylinder 29 having its periphery in supporting relation to the blade, so that by rotation its circumference is shifted in the direction of its supporting face., Opposite to the carriage 3 a standard 26 is secured on frame 1 by means of screws 26 which has two'upwardly projecting arms formed with bearings 27 and 27 accommodating a shaft 28 v 'adapted to engage registering recesses in the lateral face of the supporting cylinder 29., The pulley is, furthermore, provided .with

worm gear teeth 33l engaging a worm 34 carried by a vertical shaft 46 rotatable in a suitable vertical boring provided in the-'standard 26. On pulley 31 a cord 35 is wound having its one end attached thereto, at 31, and having its other end hanging downwardlyand provided with a weight 36. l

The carriage 3 is formed with a downwardly directed projection 37 which is recessed to Vaccommodate the end of a helical spring 38 bearing against an adjustable screw 39 inserted in the front wall of frame 1 and permitting of an adjustment of the pressure exerted by the spring on the carriage 3 which is pressed towards the right and thus kept in permanent engagement with a cam 40 mounted upon a horizontal cam shaft 41 journalled in frame 1and contin-A 46. The other arm of the bell crank 45 cai'-v ries a pawl 47 arranged 'to engage a ratchet wheel 48 rigidly attached to shaft 46 and kept in engagement therewith by action of a spring leaf 49 bearing against the pawl. The

bell crank 45 is kept in permanent contact with the push rod 44 by means of a tension spring |50 extended between a'suitable projection of frame 1 and onevarm of the bell j crank. y

The operation of the machine is as follows: A rapid rotation in the direction of the arrow of Fig. 1 is imparted to the grindshown. When the parts assume the position shown in Fig. 1 the projection 37 is 'cooperating with that section ofthe periphery of cam which is nearest to the center of the cam shat so that carriage 3 assumes its position nearest to, in fact in contact with the supporting cylinder 29. In this position a cycle of operation has just been finished. y In the course of the subsequent rotation of cam 40 through an angle of 90 the carriage 3 is moved towards its uttermost left oint and the disc 8 is withdrawn from bla e 23 permitting the blade holder 13 to be removed after a release of the clamping screws 14 and 14' and to be replaced by a similar s are holder provided with afnew blank to c sharp- .ened. v In the course of the vfurther rotation of' cam 44 through another 90 the grinding disc 8 slowly approaches the supporting cyllnder 29. In the meantime, while the section of cam 40 of the largest radius became active on the projection 37', the portion 43 of cam 42-l arrived in its operative position to the ellect I thatthe push rod has been shifted and has rocked the bell crank 45 whereby the ratchet wheel 48 has. been advanced by one tooth. A

vcorresponding turn has been imparted to worm 34 and to the supporting cylinder 29. When the section 43 hasmoved past thepush rodV 44 the latter and the bell crank are returned into their normal position by action of the tension spring 50." The purpose of the turn of the cylinder 29 preparatory to a new cycle will be explained later.

In the course of the rotation of cam 40 throughthe third quarter of a revolution'the carriage 3 is gradually advanced towards the support 30 and the new razor bladey in contact therewith until the latter is engaged by the grinding disc 8 and is sharpened by the latter and transformed into a nearly finished condition requirlng but a slight polishing the cam 40 which is driven at so low a speed` as will afford the time required f or such replacement.

In Fig. 5 we have diagrammatically illustrated the successive stages of the grinding process. In this figure the reference numeral 8 designatesthe grindingdisc and "I to V designate live successive positions of the Y grinding disc assumed in the course from its 5 outermost position I to lts innermost position V in'which the advance is completed' and another cycle of operation begins. 23

to produce the front face N, L o f the edge.

29 is the supporting cylinder, the peripheral face 'of which serves' to support the rear face of the edge and, for this purpose, is kept in intimate contact therewith and stationary thereto during the grinding process.v As

heretofore mentioned, the supporting cylinder is provided with a peripheral recess extending between the points K, L, Fig. 5. This recess is increasedin circumferential length in the course of the operation on ac" count of the stepwiseturn imparted to the support 29. Its original shape is designated by the letters K, I, O 'and is increased in every c cle by an amount corresponding to A the ang e 8 by which'the supporting cylinder is advanced in clockwise direction preparatory to each grinding cycle. Thus, in the course ofthe cycle illustrated'in Fig. 5 the recess will be enlarged by the distance G, L. The recess K, I, O is generated by the grinding disc 8 cutting into the supporting cylinder in the course of the first cycle in which the grinding disc 8 has been advanced until the edge L was situated in the central plane P of the razor blade so that a portion K, I, O, K was cut out of the cylinder. lWhen subsequently to each cycle the supporting cylinder is turned through the angle 8, the recess K, L is successively enlarged as each time another section G, H, L is cut out of the circumfer-l ence until eventually the entire cylinder is used up and a new cylinder of the prescribed diameter must be substituted. The depth QR of penetration of the grinding disc 8 depends on .the edge angle 2 a of the razor blade which los' is to be produced. The larger this angle is to be made, the lower arranged must be the blade 23 with regard tothe line S, T connecting the centers of the supporting cylinder 29 and grinding disc 8, and the more towards the 'right will bepositioned the blade kso that the grinding disc will deeper penetrate into the supporting cylinder 29 until the razor blade edge is situated in thecenter plane P.

When the grinding disc 8. approaches the position I, on it. way'toward the supporting Icylinder 29 a blank having its front in unfinished condition has been ,substituted for the razor blade which had been finished in the preceding cycle. As soon as the position II has been reached the grinding process proper nated by the 'letters B, F, C, has been ground off. In the course of this phase of the cycle the upper edge of the blade gradually approaches the point C, and coincides with the latter as soon as position VIII has been reached. The rear face C, D of the blank is preferably shaped to place the edge C beyond the central plane P for the purpose of compensating for differences in the level of the edges D, C of successive blades. In other words, as theedge C of one blade may be situated at a. higher level than the corresponding edge C of another blade on account of small differences in shape, the cross-sectional proile-with the points C and D on different sides of the central plane has been chosen. y Y

While the grinding disc advances from its position III to the position-IV the portion C, I", M, G is cut away so that the edge Vof the razor blade gradually approaches the point G where it arrives at the time IV. During this period, however, the edge C freely'extends through the space its back lacking any support whatsoever, so that a ridge of thebreadth C, G will be formed. This Lridge represents the rim leaf which yields under the pressure of the grinding disc and is bent out of the way of the latter on account of its reduced thickness and tenderness. In the moment, however, position IV edge G of therazor blade which is supported a very slight subsequent polishing treatment.

by portion H, G, D of the supporting cylinder 29-- and, for this reason, cannot yield to the grinding pressure. Consequently, the advancing grinding vdisc engages the root of the ridge leaf which is bearing against the supporting cylinder 29 and as result of the frictional engagement with the grinding disc ,is abruptly torn off.

' While the grinding disc advances from IV .to V it exerts a unitary grinding action on the supporting cylinder andthe razor blade simultaneously cutting away\ the portions G, M, N, L of the blade vand G, H, L of the supporting cylinder. In the course of this stage of theY grinding process the edge gradually advances from G to L and, in this phase, another ridge cannot be formed because the edge is continually supported while it is subjected to the grinding pressure. Hence it will appear that as soon as, or even before, the point L is reached,Y the edge will be perfectly sharp and free from any ridge so that of the razor blade will suiice to give the edge the required finish.

rIhus it is obvious that our novel method saves the time which was spent prior to our invention in removing the ridge from the edge and that the latter owing to. the matel rially reduced polishing step is not so liable to be adversely affected by the development of heat or by the polishing tool. l

It might be suggested that it would appear sufficient to-turn the supporting cylinder29,

preparatory to the phase, with the edge of its recess up to the point L only rather than up to the point G inasmuch as the ridge is removed in the moment the contact of the mechanical stresses exerted by supporting cylinder and the grinding disc occurs which occurrence might just as well be postponed until the edge has advanced todemands for a perfect razor blade. Besides,

theimavoidable wear of the grinding disc accounts for a certain irregularity of the final position of the razor blade edgewhich, accordingly, does not always exactly coincide with point L of the supporting cylinder. It follows that, while a perfect grindingdisc could perhaps he adjusted to always exactly reach the position V thereby removing the ridge even with a simple support plate U, V, L, W, Y, under ordinary conditions, for in' stance with a worn grinding disc, the position V 'would sometimes not exactly be reached so that a ridge leaf would he left.

For this reason we advance the grinding disc beyond the position IV thereby cutting into the support. 29. This operation compensates for the unavoidable small deviations in the movements of the elements of the machine which evenwith a perfect grinding disc could never be entirely eliminated. In view of these considerations we prefer, in favor of reasonable requirements regarding the exactness of the elements of the machine, to provide, as it were, a safety coefficient with regard to the supporting action, in that we support the rear face of the edge beyond the point L markingk the final location of the linished cutting edge, and in that we parv tially cut away this supported zone together with its/ support .-while the grinding disc approaches its innermost position. The portion of t-he support cut away in each cycle must, of course, be replaced preparatory to the subsequent cycle.

By the method heretofore described a cutting edge is obtained which is perfectly sharp and without any ridge, regardless of whether or not the elements ofthe machine operate quite exactly and whether the final edge exactly coincides `with the point L in the central plane l?.

Obviously, the requirement of .replacing the cut-away portion of the support prior to every cycle may be complied within a great variety of constructions. We prefer, ow-

'I ever, to use a supporting cylinder such as heretofore described as in this manner the replacement after each cycle may be accomplished in an extremely simple manner by turning the cylinder until its edge- Gr confining the recess has been moved beyond the location of the final blade edge byv such an amount which safely compensates for the effects of possible inaccuracies of the machine. i l

In producing the rear face C, D of the I the back of the blade need not be employed, it lbeing sufficient to support the original blank havin the role A, B, Z,.E by a small sup ort bla e Z,`v B', C', as in this case the con guration of the edge D is without any consequence so that the formation of a r ge.

does not matter. The function of the vsupport in this case would simply -be to prevent the blade which is given the profile ANDZE from being sprung out of shape. It may be mentioned that this preparatory stage does not form art of our invention and that the profile A ZE may be, produced in any suitable manner before the blade is subjected to our novel grinding method.

l An essential requirement for the success of our method is an intimate contact of the supporting cylinder with the rear face of the $5` blade edge or-.at least with the zone conned by the final edge. In order to avoid unreas.

onable requirements regarding the accuracy of the adjustment of the blade holder, the latter is preferably of yielding properties. In the embodiment shown for instance, it includes in its structure a spring leaf 20 permitting a small flexing vertical to its plane as well as a small turn about its vertical axis. In adjustin the bladeywe first align the blade ed e in t e desired level parallel to the axis of t e supporting cylinder and, subsequently, somew at release one of the pointed screws 15 or 16, whereu on we turn the entire blade holder about t e axis 15,` 16 to 5o bring the' blade in full contact with the supporting cylinder. Then, the released pointed j screw is tightened again so as to roperly support the block 17. On account o this adjustment the rear face of the blade edge is bearing againstthe supporting cylinder with a slight pressure vwhile-the spring leaf 20 is slightly bent to produce such pressure. This will alsobe the case, if blades of a slightly` different size are inserted as the ilexibility of 60 the spring leaf 20 compensates for small differences between the shape of the individual blades. The bladelholder, however, will be subject to small deviations from its vertical position. Ifit stands forwardly inclined with regard to its normal position,

razor blade aslmilar method of supporting the point D of the rear face is liable to come into contact with the periphery of the supporting c linder instead of the point G so that the al edge would not be supported. This may obviously be avoided by dimensioning the vradius of the supporting cylinder slightl smaller than the radius of the curvature o the profile section C, E, or, in other words, than the radius of the grinding disc employed in producing-the rear face of the blade. In thismanner, of course, a perfect contact over the entire surface of the rear*- face C, D is obviated, but an eicientsupgrt of that zone is secured in which the al edge is situated and this alone counts. In designing the diameter of the supporting vcylinder the unavoidable inaccuracies and 'differences of the individual blades are to be taken in consideration. The diameter must be made smaller` than is the diameter ofthe grinding disc producing the rear prole when it is worn oi.

In -the moment the position IV has been reached, the grinding disc engages the pe-l riphery of the supporting cylinder tending to ment with the grinding disc, however, would cause the latter to jam and perhaps even to crack. For thisreason, means must be rovided which obviate a back-lash in the ing Gear of the supporting cylinder. l

T is may -be achieved 1n the simplest manner by causing the driving members to be in permanent contact with each other in a sense contrary to their ,driving eiect. For this purpose we have provided the weight 36 which subjects shaft 28 to a torque of the same sense as that produced by the engaging grinding disc. This torque causes the teeth of the worm gear 33 to keep contact w1th the thread of the self-locking worm 34 whereby the supporting cylinder is prevented from being turned by the grinding disc. It fcllows that the advance of the supporting cylinder` through the angle 8 is, exactly speaking, performed by action of the weight 36 rather than by the wormgear 34, 33which reallv merely determines-the'exact degree of suc advance.

What we claim is:

1. In the method of sharpening the edge of a blade by keeping one face of the blade in contact with a support of non-abrasive and non-resilient material,4 while the marginal zone of the otherface of said blade is beingV ground, the improvement which resides in continuing said grinding action on amf the last mentioned face -until a portion of after each operationtorenew said supporting said support is`ground away and said edge surface.

testimony whereof we aiiixed our signahas advanced into the zone of the face which is in contact with said. support.

2. The method of sharpening the edge of a razor blade comprising the steps 0f first providing said blade with an inclined marginal -face on one side thereof, then bringing a lonsharpening machine comprising a blade supi port of a non-resilient and non-abrasive ma@ terial and a grinding wheel, means operative to press one upon the other, and a blade being interposed therebetween to be operated upon by said grinding wheel while it is bearing againstisaid support; the improvement which consists in continuing the operation of said `means until a portion of said support which has been in intimate contact with said blade has partly been ground away.

4. The method of sharpening the edge of a blade consistingof grinding one marginal face of the same while supporting the opposite marginal face of the blade by a member contacting with the blade closely adjacent the edge and -extending'beyond the same. and continuing the grinding operation until the ground surface intersects the Vsupported surface of the blade and wears away a portion ofthe supporting surface of the support.

' 5. The method ofsharpening the edges of blades consisting of successively grinding marginal faces of the same while the opposite face of the blade being sharpened is supported adjacent its edge; by a member fitting the contour of the opposite face of the blade during the grinding Operation and extending bevond the edge of the blade. and continuing the grinding operation until the ground surface intersects the supported surface of the blade and wears away a portion of the supporting surface of the support, and

renewing saidV support fitting the contour of the opposite faces. of the-blade after each.

ground surface intersects the supported sur" face of the blade and wears away a portion of the support, and rotating said support 

